1,3-Butadiene (1,3BD) is an important industrial chemical. 1,3-Butadiene is a major component of synthetic rubber, ABS (acrylonitrile-butadiene-styrene terpolymer), and latex. It is an important intermediate in production of the nylon intermediates adiponitrile and hexamethylenediamine. 1,3-Butadiene is also used to make higher value chemicals, such as cycloalkanes, cycloalkenes, 1-octene chloroprene, sulfolane, 4-vinylcyclohexene, cyclooctadiene, and cyclododecatriene. Vinylcyclohexene, for example, can be converted to styrene, which has a market of about 20 billion pounds (about 9 billion kg) per year. 1,3-Butadiene is an important co-monomer of polyethylene with a market size of over 1 billion pounds (over 450 million kg) per year. 1,3BD also can be oligomerized to form dimers, trimers, and tetramers that are useful as fuel components.
2,3-Butanediol (BDO), which may be generated as a product in some fermentation and thermochemical systems, can be used for production of bio-renewable 1,3BD. However, known methods for converting BDO to 1,3BD suffer from several disadvantages, including corrosive reagents, radioactive catalysts, and/or undesirable products. For example, BDO can be esterified with acetic acid to the diacetate, followed by pyrolysis of the diacetate to 1,3BD (Morell, Industrial and Engineering Chemistry, 37(9):877-884, 1945). This approach is complicated by the corrosive nature of the acetic acid produced, which necessitates special materials of construction.
A secondary route to 1,3BD starting with BDO is through 2-butenes, which are available either from 2-butanol by dehydration or from the 1,3-dioxolanes by acid catalyzed thermolysis. The butenes can be catalytically dehydrogenated to 1,3BD in the presence of superheated steam as diluent and heating medium (Kearby, The chemistry of petroleum hydrocarbons, ed. B. T. Brooks et al., Vol. 2., Reinhold, N.Y., 1955).
Dehydration of BDO is another route to 1,3BD. Dehydration of BDO can proceed by different mechanisms depending upon the catalyst used. Over many catalysts, including catalysts that are Brønsted acids (e.g., alumina, acidic zeolites), the product is methyl ethyl ketone (MEK).